crypto: x86/aes-xts - additional optimizations

Reduce latency by taking advantage of the property vaesenclast(key, a) ^
b == vaesenclast(key ^ b, a), like I did in the AES-GCM code.

Also replace a vpand and vpxor with a vpternlogd.

On AMD Zen 5 this improves performance by about 3%.  Intel performance
remains about the same, with a 0.1% improvement being seen on Icelake.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>